This invention relates to abrasion-resistant coating compositions, methods for making them, and articles coated with them.
More particularly, the invention provides an improved silicon-containing cured synthetic resin coating composition which forms a protective, abrasion resistant coating. Such coating compositions are sometimes referred to as silicone hard coat resins, or organo-polysiloxanes, such as the compounds produced by the condensation of hydroxy organosilicon compounds formed by the hydrolysis of organosilicon halides. The preferred silicon-containing coating compositions include products which combine colloidal silica with various acryloxy or glycidoxy functional compounds, such as acryloxy or glycidoxy functional silanes, or non-silyl acrylates.
Transparent abrasion-resistant coatings made from silicon-containing synthetic resins have been used to coat transparent plastics which do not shatter or are more resistant to shattering than glass, but which are subject to scratching and marring due to everyday contact with abrasives such as dust, cleaning equipment, and ordinary weathering. However, the application of the silicon-containing coating compositions to plastic substrates sometimes requires a primer to improve adhesion between the two materials. In some instances even the use of a primer is inadequate for good adhesion. Moreover, the application of these prior art silicon-containing coating compositions to metal surfaces has met with little success because of inadequate adhesion between the metal and the cured resin.
Even when good adhesion is obtained with the prior art silicon-containing coating compositions, the final top coat does not provide optimum hardness.
This invention provides a silicon-containing cured synthetic resin coating composition which bonds firmly to plastic and to metal surfaces to provide superior protection from abrasion and chemical attack. The coating composition of the invention includes a base coat layer of cured base coat resin, such as polyurethane, polycarbonate, polystyrene, acrylic, polyolefin, nylon, melamine, ABS, and SAN, which bonds strongly to the metal surface to be protected. A top coat layer of uncured silicon-containing synthetic resin is deposited on the cured layer of cured base coat resin, and heated to create a strong interlinking between the silicon-containing synthetic resin and the cured base coat resin. Thereafter, the silicon-containing synthetic resin is cured by heat, actinic radiation such as UV light, or particle radiation such as electron beam. The final silicon-containing cured synthetic resin coating composition can be clear or pigmented. For example, a base coat of polyurethane-containing resin can include pigment or metallic particles for decorative effect.
Practically any kind of metal surface which has been adequately cleaned can be coated in accordance with this invention. A polyurethane-containing base coat layer can be any of the well-known polyurethane coating compositions, or blends of polyurethane and acrylic resin. The layer of polyurethane or a polyurethane/acrylic mixture is coated onto a clean metal surface by any of the suitable, well-known and commercially available processes, such as spraying or electrodeposition.